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Archived

Avalanche Forecast

Nov 29th, 2021–Nov 30th, 2021
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Banff Yoho Kootenay.

Avalanche Control is planned for the Sunshine Road on Nov. 30th. No access to Mt Bourgeau or Eagle Mountain zones.

Weather Forecast

Temperatures will cool Mon night, but then warming as the next storm arrives.  Winds will rise to strong to extreme from the west and freezing levels are forecasted to be in the 2000m range. Models are forecasting ~20 cm by end of Tues, ~ 60 cm by end of Wed, and another ~ 10 cm as the system passes and cools on Thurs. Rain in valley bottoms.

Snowpack Summary

30-60 cm of snow in the last storm is reacting as a storm slab in alpine and treeline terrain. The Nov 15 crust is below this and present below 2100 m. The Nov 5 crust/facet layer exists near the ground. Snowpack depths at tree-line average 80-110 cm. Lower elevation snow (below ~ 1500 m ) is rain- soaked.

Avalanche Summary

Natural activity to size 3 as a result of the weekends storm was observed on Monday. Results from avalanche control in Kootenay showed touchy storm slabs at treeline and in the alpine with higher elevation avalanches stepping down to the deep persistent layer. At lower elevations, (below ~ 1700m), these were entraining loose wet snow.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Avalanche Problems

Storm Slabs

Recent new snow has created storm slabs that have been failing naturally and with explosives. The incoming storm will add load and make this worse. Treat all avalanche terrain with caution.

  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Watch for surface cracking and stiffer surface layers of snow. Avoid wind loaded terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2.5

Deep Persistent Slabs

With a significant new snow load we expect to see larger and more frequent avalanches occur on the basal crust and facets. These avalanches have sporadically been running full path so minimize your exposure to overhead hazards.

  • Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1.5 - 3